The internal lock body of the conventional auxiliary locks generally comprises an inner housing having two spaced through holes and a hole located therebetween; a shaft to be inserted into the hole of the inner housing and having two opposing ends, wherein one end has a circumferential groove for engaging with C-ring and the other has a transverse hole; a cover having a hole aligned with the hole in the inner housing so as to allow the shaft to pass through; a knob having an axle portion with an axial hole for fitting over one end of the shaft, wherein the axle portion has a transverse hole aligned with the transverse hole of the shaft so as to allow a pin to be inserted therein and therefore secure the shaft and the knob together.
With the lock structure as described above, since a C-ring is used to secure one end of the shaft to the inner housing, tools will be needed in assembling the locks in workshops. The assembling procedures would be very time-consuming. Furthermore, if any defect is found in a component of the locks and the component needs to be replaced during the assembling procedure, it will be found that disassembling the locks is very difficult. In addition, when installing a lock onto a door, the pin should be unfastened from the transverse hole of the knob first before the knob and the shaft can be separated. After the cover is unfastened and the inner housing is aligned with the outer housing, and two screws pass through the holes of the inner housing and thus secure the inner housing and the outer housing together, the cover is mounted, the knob is fit over the shaft, and the pin is inserted into the transverse hole after the knob is aligned with the shaft so that the knob and the shaft can be secured together. Such assembling job is complicated and difficult for ordinary users without skilled technique.